2003 Ford F150 Battery Light Comes on during acceleration

This happens off and on and does not occur all the time. This morning though the light stayed on more than usual. When I accelerate especially with a hard acceleration the battery light comes on and may stay on a few seconds. Today it stayed on but when driving I would give the pedal a tap and it would go off. Could someone tell me why this sensor light is coming on and how I might be able to correct the problem myself without paying outrageous dealer labor.

Thanks for any help and all will be appreciated